Floor surface underlayment



FIG. 1 is a perspective view of a floor surface underlayment in accordance with an embodiment of the present invention;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof; and,

FIG. 4 is a side view thereof, all other side views being mirror images thereof. 

CLAIM The ornamental design for a floor surface underlayment, as shown. 